The proposed study addresses the clinical question of the behavioral effects of iron deficiency anemia. Earlier studies have demonstrated that altered behavior and lower developmental test scores do not improve with iron therapy and that behavioral differences are still present at school entry. Building on the research team's previous work in Costa Rica and Guatemala, this study seeks to further characterize specific behavioral alterations among iron deficient infants. The study has four specific aims: (1) to characterize specific behavioral alterations in iron deficient anemic infants; (2) to determine if iron deficiency anemia has different behavioral effects in the first versus the second year of life; (3) to determine if environmental stimulation plus iron therapy corrects the behavior of infants with iron deficiency anemia; and (4) to determine of therapeutic interventions are more effective in the first or the second year of life.